Rapid transit steed control system



Oct. 3, 1967 E. STAPLES RAPID TRANSIT SPEED CONTROL SYSTEM 8Sheets-Sheet 1 Filed July 9, 1965 Exit Hahn/we.

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BY 4 AS w Hi5 ATTORNEY United States Patent Ofiiice 3,345,51 l PatentedOct. 3, 1967 3,345,511 RAPID TRANSIT SPEED CONTROL SYSTEM Crawford E.Staples, Edgewood, Pa., assignor to Westinghouse Air Brake Company,Swissvale, Pa., :1 corporation of Pennsylvania Filed July 9, 1965, Ser.No. 470,713 24 Claims. (Cl. 246-34) This invention relates to a trainspeed control system.

More specifically this invention relates to a train control system inwhich there is employed continuous train detection coupled with trainsignaling to control the speed of the train. The speed control system ofthis invention may be utilized with either alternating current or directcurrent propulsion systems in electrified territory.

The advent of modern high speed transit that utilizes electricallycontinuous rail has brought into focus new problems of train tratficcontrol. High speeds and the need to maintain closer headway betweentrains magnify the problems that arise when wayside signaling alone isutilized to control train speed. The invention to be described hereafterdoes not require wayside signaling as all the speed control signalingappears on the train where the speed control signals may be employed toautomatically control the speed of the train, or, on the other hand,allow manual control of the train. Use of the invention will alsoobviate the need for intermediate control housings by the use ofcentralized housing to provide all the needed controls. In the practiceof the invention there will be utilized rail bonds to define trackdetection circuits and these rail bonds may be of the type described inthe copending application for Letters Patent of the United States, Ser.No. 382,551, filed July 14, 1964, by Ralph Popp, for Electric InductionApparatus.

This application is an improvement over my copending application forLetters Patent of the United States, Ser. No. 382,620, filed July 14,1964, for Rapid Transit Speed Control System. The improvement in partstems from the use of an electrically continuous rail system withoutinsulated joints, thereby requiring only one impedance bond per locationand only one half the wayside audio frequency transmitters called for inmy aboveidentified application.

It is therefore an object of this invention to provide continuous trainspeed control in a rapid transit system where electrically continuousrails are employed.

It is another object of this invention to provide a speed control systemthat allows closer headway at all operating speeds and all degrees oftrack occupancy.

Another object of this invention is to provide a train speed controlsystem in which there are no conflicting speed control signals fed tothe train, thereby providing continuous speed control of the train.

Yet another object of this invention is to provide a highly efficientand economical rapid transit speed control system that makessimultaneous use of a plurality of center fed track circuits and trainspeed control circuits to accomplish this object.

In the attainment of the foregoing objects there is utilized a systemwhich includes an electrically continuous rail and a train having aspeed control receiver located on the train. The rails have a pluralityof bonds spaced along the rail with wayside transmitters for controllingtrack relays coupled to alternate bonds to form a plurality of centerfed track circuits. Each of the center fed track circuits mutuallyincludes an intermediate bond, and each of the wayside transmitters hasat least two wayside receivers for controlling track relays, onereceiver at each of the bonds immediately adjacent the bond to which theassociated wayside transmitter is fed. This center fed track circuittherefore establishes two track circuit detection sections, the trackcircuit detection sections having both an entrance end and an exit enddefined by the bonds aforementioned. Therefore, by definition everyentrance end of a track detection section is also an exit end of apreceding track detection section. While the above is true withreference to a pair of center fed track circuits it should be understoodthat where there are an uneven number of track detection sections therewill be at least one situation which will call for one waysidetransmitter and only one wayside receiver. To provide a source of trainspeed control there is a train speed control transmitter electricallycoupled to each bond along the rail. The track receivers, just noted,are interconnected through suitable control means such as relays to thetrain speed control transmitters and control the train speed controltransmitters energization. The transmission of train speed controlsignals to the train via the bonds and the rails occurs when a bond atan entrance end of a track detection section is shunted and there is asimultaneous transfer of the train speed control to the next train speedcontrol transmitter coupled to a bond at the exit end of the trackdetection section. Accordingly, the train speed control signals arealways being delivered to the rails at the exit end of a track detectionsection, which exit end as aforementioned is also the entrance end ofthe next succeeding track detection section. This speed control signalwhich is applied to the rails is picked up inductively from the rails byreceiver coils carried on the front of the train. The speed controlsignal is then fed to the train speed control apparatus on the train andthis results in a continuous speed control of the train.

The invention also contemplates the use of additional wayside receiversinterposed between the bonds along the rail to provide additional trackdetection circuits which will allow further speed control capabilitiesas when especially close headway must be maintained in station areas.

The entire system relies on the simultaneous presence in the rails ofaudio frequency energy for the track detection circuitry and train speedcontrol signals of differing frequency for control of the trains speed.

Other objects and advantages of the present invention will becomeapparent from the ensuing description of illustrative embodimentsthereof, in the course of which reference is had to the accompanyingdrawings, in which:

FIGS. 1 and 2, adapted to be arranged end to end with FIG. 1 on theleft, illustrate a circuit diagram incorporating the invention.

FIGS. 3 and 4, adapted to be arranged end to end with FIG. 3 on theleft, illustrate one form of usage for the track circuits of FIGS. 1 and2.

FIGS. 5 and 6, adapted to be arranged end to end with FIG. 5 on theleft, illustrate one situation where a train is present at a stationplatform and a second train is approaching.

FIGS. 7 and 8, adapted to be arranged end to end with FIG. 7 on theleft, illustrate a situation where a train is located at the exit end ofa station platform and a second train is approaching.

Reference is now made to FIGS. 1 and 2 in which one form of the systemembodying the invention is illustrated. In these figures there arepresent a plurality of track circuits. Basically, a track circuit, bydefinition, includes a source of electrical energy, the running rails ofa section of track, at detecting means which is usually a track relay,and a means for coupling the source and the detecting means to therails. Such is the case in FIGS. 1 and 2. From a study of these figuresit will be evident that no insulated rail joints appear along the rails17 and 18. Therefore, since one of the purposes of this invention is toprovide the ability for closer headway between trains,

there will be seen that short track circuits have been employed, butthese short track circuits do not require the use of insulated railjoints with the accompanying additional cost which arises when insulatedrail joints are used to provide boundaries for short track circuits. Inthe instant application rail bonds aid in defining many of the trackcircuits involved in this invention.

In FIG. 1, for purposes of illustration only, there is depicted a railbond with primary winding 16 between the rails 17 and 18. At the centerof the primary winding 16 is a center tap terminal 32 and a lead 33,which lead 33 may be attached to a similar center terminal of a railbond across the rails of a parallel set of tracks, not shown. In thealternative, this lead '33 may be connected to propulsion return feedersor to grounded structures which thereby aid in the reduction of thevoltage drop between the rails and between the train and the powersource. The rail bond serves the important function of equalizing thepropulsion return between the rails, while simultaneously affording aconvenient means of impressing and receiving signals to and from therails. The minimizing of the voltage drop between the train and thepower source allows the train to operate with a higher potential whichthereby enhances train operation. The maintenance of a minimum voltagedifferential between the rails is necessary to prevent interference withsignals applied to the rails as will be described hereafter. While noneof the remaining rail bonds illustrated in the remaining figures containthis center tap arrangement, it is to be understood that in the actualconstruction of this system such center tap connections would be made.This, of course, is applicable where the system to be described is usedin electric propulsion territory where the running rails are used forpropulsion return current. It should be further understood that wherethe system is employed in non-propulsion territory, that is, where therunning rails are not used for propulsion return current, the use ofcross bonding is not necessary and a suitable transformer may besubstituted to apply to and receive from the rail signals.

This invention will make use of a plurality of audio frequency trackcircuits which will provide a number of track detection sections whichwill be employed to detect the presence of a train at any point alongthe rails.

While not illustrated in the drawings, it should be understood thatconventional power supply connection terminals would be present andconnected to the various transmitters, receivers and relays to bedescribed. Since the addition of these power supply terminals would onlytend to clutter the figures, they have not been shown.

The audio frequency track circuits take the form of center fed trackcircuits. A typical track circuit arrangement can be seen in a study ofthe right-hand portion of FIG. 2 where a wayside transmitter TZW istransmitting a predetermined audio frequency. In order to distinguishbetween different frequencies transmitted, the wayside transmitters havebeen designated TZW, TSW and T4W. While the normal range of frequenciesemployed in the practice of this invention is between 1 kc. and 6 kc.,it should be understood that the invention includes within its purviewthe use of frequencies that may fall on either side of the range justnoted. The use of these frequencies that fall outside the rangeaforementioned will depend upon the parameters involved in the trackcircuits employed and the use to which the system has been designed.

The wayside transmitter TZW feeds the audio frequency energy to asecondary coil 19 which in turn is inductively coupled to a primary coil12, which primary coil is an integral part of one of the rail bondsbetween the rails 17 and 18. One of the track detection circuit paths isformed by the wayside transmitter T2W through the inductive coupling ofthe secondary coil 19 and primary coil 12, thence through the rail 17,through the primary coil 13 of another rail bond, and back along therail 18. Adjacent the primary coil 13 there is located a secondary coil22 which inductively picks up the audio frequency signal present in theprimary coil 13, and this signal passes via the leads from the secondarycoil 22 to the wayside receiver R2W2 where the audio frequency signalenergizes the wayside receiver R2W2 and related track relay TR2 tomaintain track relay TR2 in a picked-up position. The wayside receiverR2W2 is tuned to the audio frequency output of the wayside transmitterTZW.

A second train detection track circuit can be seen to the right of theprimary coil 12 which forms a part of the rail bond between the rails 17and 18. In a like manner, the audio frequency energy in the transmitterTZW is conveyed via the leads from the transmitter TZW to the secondarycoil 19 and thence inductively to the primary coil 12, along the rail17, through the primary coil 11 where the secondary coil 21 inductivelypicks up the audio frequency signal from the transmitter TZW, and thenceback along the rail 18. The wayside receiver R2Wl which is connected tothe electrical leads from the secondary coil 21 is energized when notrain is present in section 1T. With this receiver R2W1 and its relatedtrack relay TR1 energized there is seen a second track detection circuitwhich appears as a result of the center fed arrangement just described.

Since in my present invention insulated rail joints are not used exceptat interlockings, there is a short extended shunt area beyond the limitsof the track circuits defined by the rail connections for the audiofrequency transmitters and receivers hereinafter referred to as AFtransmitters and receivers. These extended shunt areas appear in theregion of the bonds containing coils 11, 12 and 13 in the center fedtrack circuit just described. In each of FIGS. 1 to 8, the arrow headswhich designate the length of track detection sections have beenpurposely extended beyond the vertical reference lines that have beenillustrated at each bond along the rails 17, 18. This extension of thearrow heads is intended to convey the presence of the extended shuntregion just discussed. This center fed track circuit just described thatincludes wayside transmitter TZW therefore has two track detectionsections which have been designated 1T and 2T. Whenever a train appearswith its wheels shunting the rails just before the rail bond containingcoil 13 is the extended shunt area, the circuit to the wayside receiverR2W2 will be shunted and the wayside receiver R2W2 and related trackrelay TR2 will be deenergized, thereby releasing or dropping the trackrelay TR2 contacts a and b. In a similar manner, when a train appears inthe track detection section 1T, there will be a similar shunting actionand the wayside receiver R2W1 and its related track relay TR1 will bedeenergized with the resulting release of the contacts a and b of trackrelay TR1.

As has been pointed out earlier there is a transmitter to provide aspeed control signal to the train via the rails, and each rail bondwhich defines a track detection section has a transmitter electricallycoupled thereto. Therefore, with reference to the track circuit justdescribed, there is seen a train speed control transmitter TC1electrically coupled via its leads to the secondary coil 21 whichinductively is coupled to the primary coil 11, which coil is a part ofthe rail bond connecting the rails 17 and 18. This transmitter TC1 whenenergized sends a signal to the rails, which signal when received by thetrain determines the speed at which the train will travel. It should beunderstood that the trains that travel on the rails just described havecoils mounted on the front of the train which inductively receive anytrain control signal present in the rails and transmit these signals tothe associated control apparatus on the train where they are utilized tocontrol the speed of the train. The precise arrangement and operation ofthese coils may be found in a description thereof in my copendingapplication for Letters Patent of the United States, Ser. No. 382,620,referred to hereinbefore. In this application there is set forth indetail the precise arrangement for receiving the train speed controlsignals which emanate from a transmitter electrically coupled to therails.

In carrying out the invention the train speed control signals from thetransmitters TC are normally of a lower frequency range than the audiofrequency signals supplied to the track detection sections. Since theimpedance of the rails to signals applied to the rails increases as afunction of the increase in frequency, the lower the frequency thelonger the track detection section may be designed. It is thereforeprudent to select a train speed control signal of 'a frequency lowerthan that frequency selected for the track detection circuitr for thereasons that follow. As has been noted there is at each bond an extendedshunt region the length of which is determined by the audio frequencyinvolved and such variable parameters as the adjustment, the length ofthe circuit, and the ballast resistance. Accordingly, for any one set ofconditions it is important that the train speed control signal reach thereceiver coils whenever the train has entered the extended shunt region.The lower frequency of the train speed control signal assures that thetrain will receive the train speed control signal because the lowerfrequency faces less impedance and can therefore travel the length ofthe extended shunt region, thereby avoiding the possibility of loss ofcontinuous train speed control. This ability to provide continuous trainspeed control effectively removes what is termed the gray area of trainspeed control, the gray area" referred to being that region in the trainspeed control system where there may arise a discontinuity in trainspeed control.

As has been pointed out, this system is comprised of a plurality ofcenter fed track circuits, each of which has been defined by rail bondsacross the rails, and each of these center fed track circuits provideswhat are to be termed a pair of track detection sections. In theinstance just described, the track detection sections are sections ITand 2T, and as has been noted, at each of the rail bonds of the centerfed track circuits there are speed control transmitters electricallycoupled to the rail bonds. Train speed control transmitter TC! isconnected to the secondary coil 21 and coupled to the primary coil 11and transmitter TC2 is connected to the secondary coil 19 and coupled tothe primary coil 12, and transmitter TC3 is connected to the secondarycoil 22 and coupled to the primary coil 13. These primary coils are partof the rail bonds that define the track detection sections IT and 2T.The rail bond which incorporates the primary coil 13 may be viewed asthe entrance end of the track detection section circuit which includesthe wayside receiver R2W2, and the exit end of this track detectionsection by definition will be at the rail bond which includes theprimary coil 12. In a like manner, the entrance end of the trackdetection section IT by definition will be at the rail bond whichincorporates the primary coil 12, and the exit end of this trackdetection section will be at the rail bond which incorporates theprimary coil 11.

The invention contemplates the incorporation of additional waysidecontrol receivers to provide additional controls to the track to allowcloser headway between trains. The precise functioning of theseadditional wayside receivers and their related track relays will bediscussed in detail more fully hereinafter.

The next center fed track circuit arrangement to the left of the centerfed track circuit arrangement just defined has a wayside transmitter TSWelectrically coupled via its leads and secondary coil 23 to the primarycoil 14 of the rail bond which interconnects the rails 17 and 18. Thistransmitter T3W supplies audio frequency energy which differs from thefrequency transmitted by transmitter T2W. It should be understood thatthe designation of 3 is meant only to symbolically indicate a differentaudio frequency from that of the transmitter T2W which is operating atan audio frequency of 2. In a like manner, the other transmitter T4Wdepicted in FIG. 1 feeding the track detection sections 6T and ST is atransmitter operating at an audio frequency which differs from thefrequency of transmitters T2W and T3W. The designations of T4W, T3-W andTZW are not meant to in any way limit the invention but are meant to beillustrative of different audio frequencies which may be used inadjacent sections of track.

The second center fed track circuit which incorporates the waysidetransmitter T3W will include the track detection sections ST and 4T. Thefirst track detection circuit to be described includes the waysidetransmitter T3W, the secondary coil 23 and its inductive coupling to theprimary coil 14 of the associated rail bond, the rails 17 and 18, andthe primary coil 15 of the rail bond in track section 4T. The secondarycoil 24 inductively receives the audio frequency energy present in therails 17 and 18 and the coil 15 of the associated rail bond. This energytravels along the leads leading from the secondary coil 24 to thewayside receiver R3W2 which is energized along with its related trackrelay TR4 to maintain the contacts a and b of track relay TR4 in apicked-up position. The second track detection circuit involved in thiscenter fed arrangement involves the track section 3T and includes thewayside transmitter TJW, the secondary coil 23, and its inductivecoupling to the primary coil 14 of the associated rail bond. Thiscircuit also includes the rails 17 and 18 and the rail bond thatincludes the primary coil 13. The audio frequency energy from thetransmitter T3W is inductively coupled to the secondary coil 22, andthis audio frequency energy energizes the wayside receiver R3W1 and inturn its related track relay TR3 to maintain the contacts a and b oftrack relay TR3 in a picked-up position.

Each of these track section-s 3T and 4T, in a similar manner to tracksections IT and 2T, has entrance and exit ends of the respective trackdetection sections 31 and 4T defined by the rail bonds which form a partof the center fed track circuit.

There is also included in this center fed track circuit the provision ofadditional wayside control in the form of intermediate wayside receiversR3W4 for track section 4T, and R3W3 for track section 3T. Thesereceivers are connected across the rails and are energized by energyreceived from the wayside transmitter T3W, which energy is translatedfrom the leads of the transmitter T3W to the secondary coil 23, thenceto the primary coil 14 of the rail bond, and along the rails 17 and 18to the leads which come from the wayside receiver R3W4. This forms acomplete circuit with the wayside receiver R3W4 and the waysidetransmitter T3-W. The receiver R3W4, which is tuned to the audiofrequency 3 of the transmitter T3-W, is energized and its related trackrelay TR4A is energized to maintain its contact a in an unreleasedposition. In a similar manner, for the track detection section 3T, thereis a wayside receiver R3W3 and this wayside receiver is energized by theaudio frequency energy present in the rails 17 and 18, this energyhaving been transmitted from the wayside transmitter TSW via its leadsto the secondary coil 23, thence to the primary coil 14 of the railbond, along the rails 17 and 18, and thence to the leads of the waysidereceiver R3W3, which receiver R3W3 is tuned to the audio frequency 3 ofthe transmitter T3W. The energization of the receiver R3W3 results inthe energization of the track relay TR3A and this track relay TRZrAmaintains its contact a in a picked-up position.

The third center fed track circuit, which includes the control of tracksections ST and 6T, has a transmitter T4W whose leads are connected to asecondary coil 26 which is inductively coupled to the primary coil 16 ofthe rail bond in a manner similar to the center fed track circuits justdescribed. The wayside transmitter T4W is operating at an audiofrequency designated as 4 and this audio frequency energy is transferredfrom the secondary coil 26 to the primary coil 16, thence along therails 17 and 18 to provide energy in the primary coil 15 of the railbond at the exit end of track section ST. The audio frequencytransmitted by T4W is of course different from that transmitted by T3'W.This energy is inductively coupled to the secondary coil 24. the energypassing along the leads which lead from the secondary coil 24 to thewayside receiver R4W1, which wayside receiver is energized along withits track relay TRS to maintain the track relay TRS contacts a and b ina picked-up position. The second circuit of this center fed arrangementincludes a rail bond with a primary coil 30 shown to the left in trackdetection section 6T. There is as with the other track detectionsections a wayside receiver R4W2 electrically coupled to the primarycoil 30 by a secondary coil 31, which secondary coil is in turnconnected by leads to the wayside receiver R4W2. The leads of a trainspeed control transmitter not shown are depicted connected to the leadsfrom the wayside receiver R4'W2. There is incorporated in this centerfed track circuit arrangement an additional Wayside control which willaffect the speed control signals and this takes the form of waysidereceiver R4W3 connected across the rails of track section ET. Thisadditional wayside receiver R4W3 is maintained in an energized conditionfrom energy transmitted by wayside transmitter T4W and transferred viathe inductive coupling between the secondary coil 26 and the primarycoil 16 of the rail bond which interconnects the rails 17 and 18. Theenergy from the transmitter T4W passes along the rails 17 and 18 to theprimary coil 30 where the energy is coupled to the secondary coil 31 andthence to the leads of the Wayside receiver R4W2 to maintain energizedthe relay TR6 to keep the track relay TR6 contacts a in a picked-upposition. The wayside receiver R4W3 and its related track relay TRSAreceive energy from the transmitter T4W which energy passes along therails 17 and 18 to the leads of the wayside receiver R4W3 to maintainenergized the relay TRSA.

It can therefore be seen that a single audio frequency transmitter, asshown in FIGS. 1 and 2, may feed two track circuits, one in eachdirection along the track. It, of course, should be noted that differentaudio frequencies must be used on adjoining track circuits butfrequencies may be repeated at suitable intervals. It should berecognized that all of the audio frequency center fed track circuitsshown in FIGS. 1 and 2 are continuously energized. It will be seen in afurther study that this will allow a continuous indication of trackoccupancy.

To be explained more fully hereinafter will be the function of the trainspeed control transmitters TCl, TCZ, TC3, TC4, TCS and TC6, each ofwhich has been electrically coupled via leads to the rail bonds thatdefine the various track sections from IT through 6T. Each of thesetransmitters applies a speed control signal to the exit end of a trackcircuit only when the track circuit is shunted and when trafficconditions ahead permit. Thus, as a train approaches a track circuit andenters what has been previously defined as the extended shunt area, atrack relay is shunted cutting off speed control energy from a trainspeed control transmitter at the entrance end of the track circuit andsimultaneously applying speed control energy from a train speed controltransmitter at the exit end of the track circuit. The signals that maybe applied will be either an authorized speed command or a limited speedcommand. These two different levels of speed are not the only possiblespeed command signals that could be made available to a train operatingon the tracks incorporating this invention. As has been pointed out,when a train occupies a detection section of a track circuit, trainspeed control energy from one of the transmitters TCl through TC6 willapply energy to the exit end of the track circuit and this may beapplied at a coded rate as has been described in my copen-dingapplication, Ser. No. 382,620, referred to hereinbefore This coded rateand carrier frequency that is transmitted will be indicative of theoccupancy of the various track sections along the rails, and theparticular frequency transmitted to the train speed control apparatusfrom the transmitters, will be indicative of speed required for thetrain for the traflic conditions present within the system. It is alsoimportant to recognize that no train speed control signaling energy willbe applied to the track circuit if the track circuit immediately aheadis occupied. The absence of a speed control signal therefore representsthe most limiting speed control command and this limiting speed controlcommand will cause the train to brake to a stop. The precise manner inwhich this occurs will be described more fully hereafter.

For purposes of explanation in this application there will only be threecab signaling conidtions utilized. They will be first, an authorizedspeed command A, and secondly, a limited speed command L, and finally ifthere is no signal at all to the rails from the cab transmitters, thiswill be indicative of the most restrictive speed and therefore willindicate to the train-carried equipment that the train should proceedinto a braking action to bring the train to a halt.

It should be understood that while throughout the remaining FIGS. 3 to 8the source of these speed control signals will not be shown, there isnormally provided a centralized control center from which the trainspeed control signals originate. This centralized control center willtherefore provide a point at which the entire system may be monitoredfor purposes of train control with reference to track occupancy and railcharacteristics (curved or straight sections of track).

A study of track detection section 1T will reveal that it can receive atrain speed control signal from transmitter TCI. This signal has beendesignated by the reference numeral L. Accordingly, a limited commandsignal L can be applied over the front contact a of track relay OTR,over the back contact a of track relay 'IRl, and thence to thetransmitter T01 and its leads which lead to the secondary coil 21, whichlimited speed control signal in coil 21 in turn impresses upon theprimary coil 11 of the rail bond the train speed control signal whichthen will appear in the rails 17 and 18, which will in turn beinductively detected by the coils which are carried by the train and inturn the signals inductively received by the coils on the train willprovide a signal to the train speed control apparatus to command thespeed designated in this particular instance L, or a limited speedcommand.

The transmitter TCZ for track detection section 21 can be set to receivea limiting speed control signal L. This circuit is completed over thefront contact b of track relay TRl via the electrical connections to theback contact a of track relay TR2, to the transmitter TC2 and thence tothe secondary coil 19 where it is inductively coupled to the primarycoil 12 of the rail bond that joins the rails 17 and 18.

In a similar manner, track detection section 31 is fed by a transmitterTC3 which may receive a limiting speed control signal L over the frontcontact b of track relay TRZ, and thence over the back contact a oftrack relay TR3, and then to the transmitter TC3 and finally to thetrack detection section 3T in a manner similar to that described withreference to track detection sections IT and 2T.

In a similar manner, track detection section 4T is fed by a transmitterTC4 and this transmitter TC4 may be alternately fed by a limitingcontrol signal L over the front contact a of track relay TR'3A, thenceover the front contact a of track relay TR4A, and next over the backcontact b of track relay TR4, and thence to the transmitter TC4 which inturn sends this limiting control signal L to the rails 17 and 18 oftrack detection section 4T. In this particular instance, there is asecond path for a limiting control signal L to the train and thislimiting control signal L can be applied over the front contact b of thetrack relay TR3, and thence over the back contact a of track relay TR4A,and next over the back contact b of track relay TR4, and thence to thetransmitter TC4 to be applied to the rails in a manner similar to thatjust described.

Track detection section T can also receive a limiting speed controlsignal L. This speed control signal will be applied and pass over thefront contact a of track relay TR4, thence over the back contact a oftrack relay TRS, and to the transmitter TCS, and thence to the rails 17and 18 via the inductive coupling between the coils 24 and in a mannersimilar to the previously described track detection sections.

The last train speed control transmitter is TC6, shown on the left-handside of FIG. 1, and it may receive either a limiting speed controlsignal L or an authorized speed control signal A. The limiting speedcontrol signal would travel over the front contact a of track relayTRSA, and thence over the back contact b of track relay TRS, and thenceto the back contact a of track relay TR6, and then to the transmitterTC6 to apply a limiting control signal L to the rails in a manner thathas been previously described.

It will be understood that track detection section GT is some distancefrom the station platform designated to the right in FIG. 2, and as suchrepresents only the first track detection section that appears as therails pass away from the train station, and therefore in this section 6Tand the sections that would appear to the left of 6T there is a need foran authorized speed control to permit the train to travel at theauthorized speeds along the rails. Therefore, it can be seen that anauthorized command signal designated A may be fed over the front contactb of track relay TRS, thence over the back contact a of track relay TR6and thence to the transmitter TC6 to be fed to the rails as has beendescribed earlier. This would provide an authorized speed command A toappear in the rails 17 and 18 whereafter the signal would be inductivelyreceived by the coils of the train and thence translated to the train toprovide an authorized command control signal to permit the train toproceed at the authorized speed.

It should be understood that while this application sets forth anenvironment in which a train or trains are entering a train station, thesystem is equally applicable to curved sections of track where thespeeds of the train must be reduced in order that the train maintainsthe proper speed for the track conditions involved. Therefore, a systemsimilar to this one in which there are limited or authorized speedcontrols fed to track detection sections in curved sections of the railsmay be employed to slow the train dependent upon the part of track curveencountered. Employment of the system simultaneously al lows a controlof headway between trains on all sections of track whether curved,straight, or entering a station area.

It should also be understood that while the invention is set forth in anenvironment where a train stops or is slowed as it passes a station,this is not intended to limit the actual use of the system. Theinvention therefore contemplates the use of train speed control signalswhich will allow a train to maintain authorized speed through a stationwith stops for example at every other station. In other words any trainspeed control pattern may be established at a centralized control pointdependent on the use to which the system is sought to be adapted. Thetrain speed control signals to the rails via the inputs A and Lthroughout FIGS. 1 to 8 may or may not be coded in the manner set forthin my copending application, Ser. No. 382,620, hereinbefore referred to,in which this coded arrangement was set forth in some detail.

Operation of the system In describing the operation of the system,reference is now made to FIGS. 3 and 4, in which there is illustratedthe system depicted in FIGS. 1 and 2 with the addition of a train Xshown in dotted lines in a number of positions along the rails 17 and18, the positions being X1, X2,

X3, X4, X5, X6 and X7. The precise manner in which the system operateswill now be described with the train X approaching the station from theleft-hand side of this figure passing to the right. When the train X isin the X1 position, the wheels of the train shunt the rails 17 and 18and in so doing deenergize the circuit that includes the waysidetransmitter T4W which has impressed on the rails 17 and 18 the audiofrequency energy which has been energizing the wayside receiver R4W2 andits related track relay TR6. With the wheels across the rails 17 and 18,the wayside receiver R4W2 is deenergized and the track relay TRfireleases, thereby closing the back contact a of relay TR6. It willtherefore be seen that a circuit is completed between the authorizedspeed control input A over the front contact b of track relay TRS andthe back contact a of track relay TR6, thence to the transmitter TC6,which places upon the rails the authorized speed command A via theinductive coil 26 and the related primary winding 16 of the rail bond.This transmitter control signal travels along the rails 17 and 18 whereit is inductively picked up by coils (not shown) carried on the front ofthe train and thence to a train speed control apparatus 27.

As the train passes from position X1 to position X2, the front of thetrain as it approaches the rail bond which includes the primary coil 16enters what is termed an extended shunt area, that is, a region shortlybefore the rail bond in which the wheels of the train actually shunt theenergy being delivered from the wayside transmitter through the wheelsof the train rather than allowing the normal energy path through therail bond to occur. This extended shunt area varies in length dependingupon the signaling frequency, the length of the circuits, and theballast resistance present in the tracks at the rail bond location. Itshould be understood that these extended shunt areas, which typicallymay vary in the region of 30 feet or more, will appear at either side ofthe rail bond. For purposes of illustration only, each of the trainsdepicted proceeding from left to right in this figure will be shownexactly at the rail bond for purposes of explaining how the relatedwayside circuitry functions to produce a command control signal to bedelivered to the rails which in turn control the speed of the train.

When the train is in position designated X2, the front wheels of thetrain will shunt the energy between the rails 17 and 18, the energybeing delivered from the wayside transmitter T4W. Therefore, the waysidereceivers R4W3 and R4W1, which are in track detection section 5T, willbe deenergized and their related track relays TRSA and TRS will also bereleased due to the deenergization of their respective receivers. Thetrain in this position is now entering the entrance end of trackdetection section 5T, while simultaneously leaving the exit end of trackdetection section 6T. When it does so the track relay TRSA, as has beennoted, releases and its contact a opens, thereby removing anypossibility for the limited speed control command signal L to be appliedto the track detection section 6T immediately behind the train in the X2position. It should be noted also that since track relay TRS is alsoreleased, the authorized speed control signal A cannot be applied to thetransmitter TC6. The deenergization of track relay TRS causes theclosing of back contact a of the relay TRS. It will be seen that thereis then a complete circuit for the limited speed command control signalL over the front contact a of track relay TR4, thence over the backcontact a of track relay TRS, and thence to the transmitter TCS whichdelivers the limited speed control signal L to the secondary winding 24,thence to the primary winding 15 of the rail bond, and through the rails17 and 18. This limited speed control signal travels along the rails andis inductively received by the coils (not shown) mounted in the front ofthe train, and this signal, that is, this limited control signal L isdelivered to the train speed control apparatus 27 of the train andautomatically produces a limited speed command which causes the brakingof the train to reduce the speed from that of an authorized speed tothat of a limited speed.

As the train continues from left to right and enters position X3, thefollowing track circuits are effected. As the train enters the entranceend of the track detection section 4T, the train is therefore enteringthe second center fed track circuit which has as its source of audiofrequency energy wayside transmitter T3W. Therefore, the train wheelswhich are at or near the rail bond which carries the primary coil 15,shunt the wayside receiver R3W2, thereby deenergizing this receiver andits related track relay TR4, which opens the front contact a of trackrelay TR4 and closes the back contact b of track relay TR4. It willtherefore be seen that there is now a complete circuit which produces alimited speed control L. This speed control L appears over the frontcontact a of track relay TRSA, thence over the front contact a of trackrelay TR4A, and thence over the back contact b of track relay TR4, andthence to the transmitter TC4. The signal, which is a limited speedcontrol signal, passes through the electrical leads from the transmitterTC4 to the rails where this signal is inductively coupled via thesecondary winding 23 to the primary winding 14 of the rail bond and tothe rails, as just noted, and thence to the pickup coils (not shown) ofthe train in position X3, the speed control signal then being deliveredto the train speed control apparatus 27 of the train.

When the train is in position X4, the intermediate wayside relay R3W4 isshunted and the track relay TR4A of this wayside receiver isdeenergized. It will be seen that, even though this wayside receiverR3W4 has been deenergized, there will continue a limited speed controlto the cab of the train and this limited speed control will appear overthe front contact b of track relay TR3, thence over the back contact aof track relay TR4A, thence over the back contact b of track relay TR4,and thence to the transmitter TC4 to apply a limiting control signal tothe rails in the same manner that has just been described.

When the train enters position X5 the wheels of the train will shunt thecircuits that are fed by the wayside transmitter T3W in the trackdetection section 3T. Therefore, the wayside receiver R3W3 and itsrelated track relay TRSA will be deenergized as will be the waysidereceiver R3W1 and its related track relay TR3. This will result in theopening of the normally closed contact a of track relay TR3A and theclosing of the normally opened contact a of track relay TR3, as well asthe opening of the normally closed contact b of track relay TR3. Thisresults in a limited speed control signal L over the following circuit.The limiting speed control signal L will therefore follow a path overthe front contact b of track relay TRZ, thence over the back contact aof track relay TR3, and thence to the transmitter TC3 which will thenapply the limited speed control signal via the coils 22 and 13 to therails 17 and 18 in a manner similar to that previously described. Thetrain, therefore, in position X5 will receive a limiting control signal,which signal will be the same as the limiting control signals previouslyreceived as the train approached the station.

Upon reaching the position designated X6 the train will be leaving thetrack detection section ST and entering the track detection section 2T,which will result in the shunting of the rails 17 and 18 to produce thedeenergization of wayside receiver RZWZ which is normally energized fromthe center fed circuit which has as its source of energy the waysidetransmitter T2W. The deenergization of the wayside receiver R2W2 and itsrelated track relay TRZ will close the normally opened contact a oftrack relay TRZ and open the normally closed contact b of track relayTRZ. This will result in the following limited speed control signalcircuit. The limiting speed control signal circuit will be over thefront contact b of track relay TRl, thence over the back contact a oftrack relay TR2, and thence to the transmitter TCZ which will apply thislimiting control speed signal to the rails in the same manner previouslydescribed. It can therefore be seen that the train in position X6 iscontinuously receiving as it enters and leaves the track detectionsection a limiting control signal, and as the train enters one sectionand leaves another there is a continuity of limited speed controlsignals constantly being applied to the rails to be inductively receivedby the pickup coils of the train. The coils of the train in turn allowthe transmission of the limited control signal to the train speedcontrol apparatus 27 of the train to produce the requisite automaticcontrol of the train speed.

There is one further position shown where the train is near the end ofthe station platform and is in position X7. When the train is in thisposition, the train has now entered the entrance end of track detectionsection IT and in so doing has shunted the energy being delivered by thewayside transmitter TZW to the rails 17 and 18, and in so doing hasdeenergized the wayside receiver RZWI and its related track relay TRl,which results in the closing of the normally open contact a of trackrelay TRl and the opening of contact b of the normally closed contact oftrack relay T R1. Therefore, it will be seen that a limited controlsignal will be applied to the rails to be delivered to the train inposition X7 over the following circuit. The limiting control signal willbe applied to and over the front contact a of track relay OTR, thenceover the back contact a of track relay TRI and thence to the transmitterTCl which in turn delivers the limited speed control signal to the railsin a manner similar to that described with reference to track detectionsections 2T through 6T.

Reference is now made to FIGS. 5 and 6 which depict the same trackcircuit system illustrated in the earlier figures just described. Thisset of figures is intended to convey the functional operation of thetrack relays that are at the wayside and the related train speed controltransmitter signals as they are applied to the rails to command thecontrol of the train speed as it enters a station where there is alreadya train stopped on a section of track. It should be understood thatwhile these figures illustrate what appears to be a static condition fora number of positions of a train entering a station, it is intended toconvey the concept that the system is a dynamic system in which trainsare constantly moving and the trains depicted in these two figures aremeant to be viewed as being stopped instantaneously in their transitalong the rails. For purposes of explanation the system will bedescribed as in a static state for purposes of easing the explanation ofthe related circuitry.

In FIGS. 5 and 6 there are two trains depicted. The train W with itstrain speed control apparatus 29, which is stopped in track detectorsection 3T, is shown in heavy lines, while a train approaching thestation from left to right designated train V, shown in positions V1, V2and V3, is a train approaching the now stopped train W. With train Wstopped where it is, the wheels of the train across the rails 17 and 18shunt the center fed track circuit which includes the track section 3T.The transmitter which feeds the audio frequency signals to this sectionof rail is transmitter T3W, and since the train wheels shunt the railsbefore the wayside relay receiver R3W3, the wayside receiver R3W3 istherefore deenergizted along with its related track relay TR3A, and thecontact a of rack relay TR3A is opened. Also, the wayside receiver R3W1is shunted by the presence of the train W in the track section ST. Thetrain W shunts the rails 17 and 18 and thereby deenergizes the waysidereceiver R3W1 and its related track relay TR3. This results in theclosure of the back contact a of track relay TR3 and the opening of thefront contact b of track relay TR3. It can therefore be seen that alimiting control signal L will be then applied across the front contactb of track relay TR2, thence across the back contact a of track relayTR3, and thence through the transmitter TC3 where this limiting signalwill be applied to the rails via the coils 22 and 13 in a mannerpreviously described. This limiting control signal of course is beingapplied when the train is in its dynamic or moving state. It shouldagain be noted that the contact a of track relay TR3A is now open aswell as the contact b of track relay TR3.

As the train V in position V1 approaches from left to right in thisfigure and into position V1, the wheels of the train will shunt therails in the track section 6T and therefore the transmitter energy fromwayside transmitter TW4 will not be received by the wayside receiverR4W2 and this wayside receiver will then be deenergized along with itsrelated track relay TR6. This will cause the contact a of track relayTR6 to be released and come in contact with the back contact of rackrelay TR6. It can then be seen that there is an authorized speed commandsignal A which will be then applied across the front contact b of trackrelay TR5, thence over the back contact a of track relay TR6, and thenceto the transmitter TC6 where this authorized speed command signal A willbe delivered to the rails and the train speed control apparatus 28 in amanner similar to that previously described. This authorized signal whenapplied to the rails will be received by the train V in the V1 positionand this will permit the train to maintain its authorized speed at amaximum speed in this section of track.

When the train passes through track section 6T and enters the entranceend of section T, the following circuits will be effected. Since thetrain V in position V2 effectively shunts all the energy from thewayside trans mitter TW4 through the wheels of the train, intermediatewayside receiver R4W3 will be deenergized along with its track relayTRSA and the contact a of track relay TRSA will be opened. Since thewheels shunt the rails and all the energy from the transmitter TW4passes through the wheels of the train when the train is in position V2,the wayside receiver R4W1 and its related track relay TR5 will also bedeenergized, thereby releasing the track relay and closing the backcontact a of track relay TR5. The release of the track relay TR5 alsocauses the back contact b of track relay TR5 to close. This will thenprovide a limited speed control signal L to be applied over thefollowing path. The limiting speed control signal L will travel alongthe front contact a of track relay TR4, thence over the back contact aof track relay TR5, to the transmitter TCS where this limited speedcontrol signal L will then be applied to the rails and received by thetrain speed control receiver 28 in a manner previously described. It cantherefore be seen that as the train V leaves position V1 and entersposition V2 the signal fed to the rails to control the speed of thetrain changes from an authorized speed control A or maximum speed to alimited speed control signal L. The train V then proceeds toward thetrain W which is standing in the station. When the train V approachesthe exit end and enters the position shown at V3 at the exit end oftrack section 51, the following circuits will be effected. Since thetrain has its wheels shunting the rails in the vicinity of the rail bondat this position, the wayside receiver R3W2 which is normally fed energyfrom the transmitter T3W is deenergized along with its related trackrelay T R4 to open the front contact a and close the back contact b oftrack relay TR4. The following speed control circuit will then occur. Itshould he remembered that the contact a of track relay TR3A and thecontact b of track relay TR3 have both been opened as a result of thetrain wheels of the train W shunting the rails in the track section 3T.Accordingly, there will be no path which the limiting speed controlsignals L may follow to reach the transmitter TC4, and since thistransmitter TC4, which feeds the track section 4T, is the only means ofspeed control to the rails and thence to the train speed controlapparatus 28 of the train, no signal will therefore be applied to therails and this will create at the train the most limited or restrictivecondition, which is that of braking. In the absence of a signal, as hasbeen already noted, the most restrictive condition is applied and thetrain automatically receives a braking action in order to bring thetrain to a halt before collision with the train W in the station.

It can be seen that as this train V approaches the station and while inposition V1 there is an authorized speed control and as it proceedstoward the station area decreasing the headway between the trains V andW, the speed control to the rails automatically changes from that of anauthorized speed control signal A in position V1 to a limited speedcontrol signal L in position V2 and next to the most restrictive speedcontrol situation in position V3, at which time the train begins toenter the braking operation to bring the train to a halt.

FIGS. 7 and 8 represent a second set of circumstances in which the trainis in the station or just leaving the station and a second train isapproaching from left to right. In these figures, the train that isapproaching from left to right is designated Y, and takes the positionsY1 through Y5, while the train departing from the station or standing inthe station is designated Z. With the train Z in this position, thewayside transmitter TZW that feeds this track detection section has itsenergy, which has been fed to the rails, shunted through the wheels of atrain and thereby causes the deenergization of the wayside receiver R2W2which is normally fed from this transmitter T2W. This deenergization ofthe wayside receiver R2W2 causes the release of related track relay TR2.This release closes the back contact a and opens the front contact b oftrack relay TR2. The train speed transmitter control signal in thisparticular instance will therefore be a limiting speed control signal Lwhich will appear over the front contact b of track relay TRl and thenceover the back contact a of track relay TR2 to the transmitter TCZ andthence to the rails and the train speed control apparatus 29 in a mannerearlier described.

A study will now be made of the train Y as it approaches from left toright and enters the position Y1 depicted in the left-hand portion ofFIG. 7. When the train Y is in the position Y1, the track detectionsection 6T which the train occupies has the rails shunted and in sobeing shunted deenergizes the wayside receiver R4W2, which receiver R4W2is normally being fed from the wayside transmitter T4W. This shuntingcauses the related track relay TR6 of the wayside receiver R4W2 to bedeenergized and released, and therefore the contact a comes to rest onthe back contact of track relay TR6. Accordingly, there is applied tothe transmitter TC6 an authorized speed control signal A over the frontcontact b of track relay TR5, thence over the back contact a of trackrelay TR6, and thence through the transmitter TC6 where this authorizedspeed control signal is applied to the rails and the train speed controlapparatus 30 in a manner earlier described. The train Y therefore inposition Y1 is receiving an authorized speed control signal A and maymaintain its maximum speed in section 6T of the rails.

When the train enters the position Y2, the following circuits areeffected by the presence of train wheels shunting the rails. Thetransmitter T4W, which normally feeds its energy to the rails to controlthe wayside receivers R4W1 and R4W3, has been efiectively shunted by thepresence of the wheels across the rails in train position Y2. Therefore,no energy from the transmitter T4W is being passed along the rails 17and 18 to energize the receivers R4W3 and R4W1. This results in thedeenergization and the release of track relays TR5A and TR5 with theconcomitant opening of the track relay contact a of relay TR5A and theclosing of the contact a of track relay TR5 and the shifting of thecontact b from the front contact to the back contact b of track relayTR5. This results in the limiting speed control signal L being appliedacross the front contact a of track relay TR4 and thence over the backcontact a of track relay TR5, and thence to the transmitter TC5 wherethis limiting speed control signal is applied to the rails and the trainspeed control apparatus 30 in a manner similar to that earlierdescribed. Therefore, the train in position Y1 receives a limitedcontrol speed signal L.

When the train enters the track detector section 4T as it exits tracksection 4T and is now in the position Y3, the following circuits will beeffected by the shunting action of the wheels across the rails. Thetrack relay receiver R3W2, which is normally receiving energy from thetransmitter T3W, is deenergized by the shunting action of the wheelsacross the rails and its related track relay TR4 releases, therebyopening the front contact a of track relay TR4 and closing the backcontact b of track relay TR4. This produces the following limited speedcontrol circuit path to the transmitter TC4. This speed control signal Lpasses over the front contact a of track relay TR3A, thence over thefront contact a of track relay TR4A, and neXt over the back contact b oftrack relay TR4 and thence to the transmitter TC4 where this limitedspeed control signal is applied to the rails and fed to the train speedcontrol receiver 30 in position Y3. The train, therefore, receives thelimiting speed control signal and continues in the manner it was when itreceived the signal in position Y2, which is in a limited speed controloperation.

When the train reaches the position Y4 in track detection section 4T,the following circuits are effected. The wayside receiver R3W4, which isnormally energized by the wayside transmitter T3W, has its circuitshunted and therefore the wayside receiver R3W4 is deenergized alongwith its related track relay TR4A. The release of track relay TR4A,thereby closes the back contact a of track relay TR4A and the followingspeed control signal path to the transmitter TC4 is present. Thelimiting control signal L passes over the front contact b of track relayTRS, thence over the back contact a of track relay TR4A, next over theback contact b of track relay TR4, and thence to the transmitter TC4.This limiting speed control signal is then applied to the rails andthence to the train speed control apparatus 30. The train in position Y4is therefore receiving, as it was in positions Y2 and Y3, a limitingspeed control signal.

When the train moves from position Y4 in the center of track detectorsection 4T to the exit end of track detection section 4T and into theentrance end of track detection section 3T, the following circuits areefiected.

With the train in position Y5 it should be recognized that the trainspeed control, if any, will have to come from the transmitter TC3, andat this time it should be recalled that with the train Z in the positionin the middle of track detector section 2T, the wayside receiver R2W2and its related track relay were deenergized by the shunting action ofthe train wheels across the rails, thereby opening the front contact I)of track relay TR2. This in effect stops a limited speed control signalfrom being applied to the cab transmitter TC3. Therefore, the trackdetection section 3T, when a train is in the position of train Z, has notrain speed control energy signal being delivered to this section oftrack, and therefore with the train in position Y5, there will be notrain speed control signal delivered to the rails, and the train inposition Y5 will be in the most limited speed control situationpossible, namely, that of a braking condition to bring the train to ahalt.

In these two FIGS. 7 and 8, as well as in FIGS. 5 and 6, there has beenillustrated the situation where two trains are on the trails at the sametime with one train in the station, and it is evident that this system,just described, provides for an automatic speed control of both trainsespecially the train approaching from the left to the right when a trainis already within a station or leaving a station. The description ofthese FIGS. 5 through 8 therefore illustrates the dynamic manner inwhich the speed control signals are shifted from an exit end to an exitend of successive track detection sections as a train passes along therails toward the station which is occupied by another train. It can beseen that the trains go through an authorized speed control condition,thence to a limited speed control, and next when the trains approach tooclose to each other, relatively speaking that is, the system providesfor the automatic removal of train speed signal control energy to therails, thereby imposing the most restrictive condition to the rails thatcan be applied.

While the present invention has been illustrated and disclosed inconnection with the details of illustrative embodiments thereof, itshould be understood that those are not intended to be limitative of theinvention as set forth in the accompanying claims.

Having thus described my invention, what I claim is:

1. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having speed control receiver meansto receive a train speed control signal from said rails,

(a) first, second and third bonds interconnecting said rails, each bondhaving a train speed control trans mitter means electrically coupled tosaid bond to provide train speed control signals to said rails, and saidsecond bond having a wayside transmitter electrically coupled to saidsecond bond,

(b) said first and third bonds having wayside receivers tuned to theoutput of said wayside transmitter and electrically coupled thereto tocontrol said train speed control transmitter means so that when saidtrain passes said first bond and then said second bond, said train speedcontrol transmitter means at said first bond and said second bondrespectively cease to control said train and there is a simultaneoustransfer of speed control to said train speed control transmitter meansat said second bond and then said third bond to thereby provide acontinuous speed control to said speed control receiver on said train.

2. The train speed control system of claim 1 wherein there is positionedintermediate said bonds at least one additional wayside receiverelectrically coupled to said rails to establish an intermediate controlpoint between said bonds, said additional wayside receiverinterconnected to said train speed control means so that when saidadditional wayside receiver is shunted by said train there is providedan additional speed control to said speed control receiver means on saidtrain.

3. The train speed control system of claim 1 wherein said waysidereceivers are continuously energized by said wayside transmitter untilshunted by said train while said train speed control transmitter meansat said second bond and said third bond are only energized when saidtrain shunts said rails deenergizing said wayside receivers at saidfirst bond and said third bond respectively.

4. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having a speed control receivermeans to receive a train speed control signal from said rails,

(a) first, second and third bonds interconnecting said rails each bondhaving a train speed control transmitter means electrically coupled tosaid bond to provide train speed control signals to said rails, and saidsecond bond having a wayside transmitter electrically coupled to saidsecond bond,

(b) said first, second and third bonds having an extended shunt regionalong said rails on the train approach side of said bonds,

(c) said first and third bonds having wayside receivers tuned to theoutput of said wayside transmitter and said wayside receiverselectrically coupled thereto to control said train speed controltransmitter means so that when said train enters said extended shuntregion of said first bond and shunts said rails, said train speedcontrol transmitter means at said first bond ceases to control saidtrain and there is a simultaneous transfer of speed control to saidtrain speed control transmitter means at said second bond to therebyprovide a continuous speed control signal to said speed control receiveron said train.

5. The train speed control system of claim 4 wherein there is positionedintermediate said bonds at least one additional wayside receiverelectrically coupled to said rails to establish an intermediate controlpoint between said bonds, said additional wayside receiverinterconnected to said train speed control means so that when saidadditional wayside receiver is shunted by said train there is providedan additional speed control to said speed control receiver means on saidtrain.

6. The train speed control system of claim 4 wherein said waysidereceivers are continuously energized by said wayside transmitter untilshunted by said train while said train speed control transmitters atsaid second bond and said third bond are only energized when said trainenters said extended shunt region of said first bond and said extendedshunt region of said second bond respectively.

7. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having a speed control receivermeans to receive a train speed control signal from said rails,

(a) a plurality of bonds interconnecting said rails, said bonds defininga plurality of track detection sections, each bond having a train speedcontrol transmitter means electrically coupled to said bonds to providetrain speed control signals to said rails, wayside transmitterselectrically coupled to alternate bonds, each wayside transmitter havingat least two way side receivers tuned to the output of said waysidetransmitters and wayside receivers electrically coupled to each of theimmediately adjacent bonds to control said train speed controltransmitters so that when said train passes a bond entering a trackdetection section said train shunts said rails, said train speed controltransmitter means at said bond crossed by said train ceases to controlsaid train and there is a simultaneous transfer of speed control to saidtrain speed control transmitter means at the next bond along said rails.

8. The train speed control system of claim 7 wherein there is positionedintermediate said bonds at least one additional wayside receiverelectrically coupled to said rails to establish an intermediate controlpoint between said bonds, said additional wayside receiverinterconnected to said train speed control means so that when saidadditional wayside receiver is shunted by said train there is providedan additional speed control to said speed control receiver on saidtrain.

9. The train speed control system of claim 7 wherein said waysidetransmitters have different audio frequency outputs which are in aselected order to thereby avoid possible mutual interference with saidtuned wayside receivers, and said train speed control transmitter meanswhich are coupled to said bonds have different frequency outputsdependent on the occupancy of said rails and the track detection sectionshunted.

10. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having a speed control receivermeans,

(a) a plurality of bonds interconnecting said rails and spaced alongsaid rails, said bonds defining a plurality of track detection sections,

(b) wayside transmitters electrically coupled to alternate bonds,

() each wayside transmitter having at least two wayside receivers tunedto the output of said wayside transmitters and electrically coupled toeach of the immediately adjacent bonds,

(d) train speed control transmitter means electrically coupled to eachof said bonds and controlled by said wayside transmitters so that whensaid train passes a bond entering a track detection section said trainshunts said rails, said train speed control transmitter means at saidbond passed by said train ceases to control said train and there is asimultaneous transfer of speed control to said train speed control meansat the next bond along said rails.

11. The train speed control system of claim 10 wherein there ispositioned intermediate said bonds at least one additional waysidereceiver electrically coupled to said rails to establish an intermediatecontrol point between said bonds, said additional wayside receiverinterconnected to said train speed control transmitter means so thatwhen said additional wayside receiver is shunted by said train there isprovided an additional speed control to said speed control receiver onsaid train.

12. The train speed control system of claim 10 wherein said waysidetransmitters have different audio frequency outputs which are in aselected order to thereby avoid possible mutual interference with saidtuned wayside receivers, and said train speed control transmitter meanswhich are coupled to said bonds have different frequency outputsdependent on the occupancy of said rails and the track detection sectionshunted.

13. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having a speed control receivermeans to receive a train speed control signal from said rails,

(a) a plurality of bonds interconnecting said rails and spaced alongsaid rails, said bonds defining a plurality of track detection sections,each section having an entrance end and an exit end,

(b) wayside transmitters electrically coupled to alternate bonds,

(c) each wayside transmitter having at least two wayside receivers tunedto the output of said wayside transmitters and electrically coupled toeach of the immediately adjacent bonds,

((1) train speed control transmitter means electrically coupled to eachof said bonds,

(c) said wayside receivers controlling said train speed controltransmitter means so that when said train enters said entrance end of atrack detection section and shunts said rails, said train speed controltransmitter means at said entrance end of said track detection sectionceases to control said train and there is a simultaneous transfer ofspeed control to said train speed control transmitter means at said exitend of said track detection section.

14. The train speed control system of claim 13 wherein there ispositioned intermediate said bonds at least one additional Waysidereceiver electrically coupled to said rails to establish an intermediatecontrol point between said bonds, said additional wayside receiverinterconnected to said train speed control transmitter means so thatwhen said additional track relay receiver is shunted by said train thereis provided an additional speed control to said speed control receiveron said train.

15. The train speed control system of claim 13 wherein said waysidetransmitters have different audio frequency outputs which are in aselected order to thereby avoid possible mutual interference with saidtuned wayside receivers, and said train speed control transmitter meanswhich are coupled to said bonds have different frequency outputsdependent on the occupancy of said rails and the track detection sectionshunted.

16. A train speed control system for use in a system having electricallycontinuous rails and a train thereon having a speed control receivermeans to receive a train speed control signal from said rails,

(a) a plurality of bonds interconnecting said rails and spaced alongsaid rails, said bonds defining a plurality of track detection sections,each section having an entrance end and an exit end,

(b) wayside transmitters electrically coupled to alternate bonds,

(c) each wayside transmitter having at least two wayside receiverselectrically coupled to each of the immediately adjacent bonds,

(d) train speed control transmitter means electrically coupled to eachof said bonds,

(e) each of said bonds having an extended shunt region along said railson the train approach side of said bonds,

(f) said wayside receivers controlling said train speed controltransmitter means so that when said train enters said extended shuntregion at an entrance end of a track detection section and shunts saidrails, said train speed control transmitter means at said entrance endof said track detection section ceases to control said train and thereis a simultaneous transfer of speed control to said train speed controltransmitter means at said exit end of said track detection section.

17. The train speed control system of claim 16 wherein there ispositioned intermediate said bonds ,at least one additional Waysidereceiver electrically coupled to said rails to establish an intermediatecontrol point between said bonds, said additional wayside receiverinterconnected to said train speed control transmitter means so thatwhen said additional wayside receiver is shunted by said train there isprovided an additional speed control to said speed control received onsaid train.

18. The train speed control system of claim 16 wherein said waysidetransmitters have different audio frequency outputs which are in aselected order to thereby avoid possible mutual interference with saidtuned wayside receivers, and said train speed control transmitter meanswhich are coupled to said bonds have different frequency outputsdependent on the occupancy of said rails and the track detection sectionshunted.

19. A train speed control system for use on electrically continuousrails,

(a) a train on said rails having a speed control receiver thereon,

(b) a plurality of bonds spaced along said rail,

(c) wayside transmitters electrically coupled to alternate bonds to forma plurality of center fed track circuits each mutually including anintermediate bond,

(d) each wayside transmitter having at least two wayside receivers tunedto the output of said wayside transmitter and said wayside receiverselectrically coupled to each of the immediately adjacent bonds,

(e) each of said center fed track circuits forming two track circuitdetection sections, each section having an entrance end and an exit enddefined by said bonds,

(f) train speed control transmitter means electrically coupled to eachof said bonds,

(g) said track relay receivers controlling said train speed controltransmitter means so that when a bond and related track circuit at anentrance end of a track circuit detection section being fed a traincontrol signal is shunted there is a simultaneous transfer of speedcontrol to said exit end train speed control transmitter means tothereby provide a continuous speed control signal to said speed controlreceiver on said train.

20. The train speed control system of claim 19 wherein there ispositioned intermediate said bonds of said track circuit as least oneadditional Wayside receiver electrically coupled to said rails toestablish an additional intermediate track circuit which intermediatetrack circuit will include one of said alternate bonds and relatedwayside transmitter, said additional wayside receiver interconnected tosaid train speed control transmitter means so that when said additionalwayside receiver is shunted by said train there is provided anadditional speed control to said speed control receiver on said train.

21. The train speed control system of claim 19 wherein said waysidetransmitters of said center fed track circuits have differing audiofrequency outputs which are in a selected order to thereby avoidpossible mutual interference with said tuned wayside receivers of eachof said 20 center fed track circuits, and said train speed controltransmitter means which .are coupled to said bonds have differentfrequency outputs dependent on the occupancy of said rail and whichtrack circuit is shunted.

22. The train speed control system of claim 19 wherein said waysidereceivers are continuously energized by said wayside transmitters untilshunted by said train while said train speed control transmitter meansare consecutively energized at each bond as said bond immediatelypreceding said energized speed control transmitter means is shunted bysaid train.

23. A train speed control system for use in electrified territory, saidsystem having electrically continuous rails through which electricpropulsion return current flows and a train thereon having a speedcontrol receiver means to receive a train speed control signal from saidrails,

(a) a plurality of bonds interconnecting said rails and spaced alongsaid rails, each of said bonds capable of equalizing the electricpropulsion return current in said rails and having a primary coil and asecondary coil inductively coupled to said primary coil, said primarycoil electrically connecting said rails, said bonds defining a pluralityof track detection sections, each section having an entrance end and anexit end, said bonds serving as a signal transfer means to and from saidrails,

(b) wayside transmitters electrically connected to a secondary windingof said bonds at alternate bonds,

(c) each Wayside transmitter having at least two wayside receivers tunedto the output of said wayside transmitters and each electricallyconnected to a secondary winding of the immediately adjacent bond,

(d) train speed control transmitter means electrically connected to thesecondary Winding of each of said bonds,

(e) said wayside receivers controlling said train speed controltransmitter means so that when said train enters said entrance end of atrack detection section and shunts said rails, said train speed controltransmitter means at said entrance end of said track detection sectionceases to control said train and there is a simultaneous transfer ofspeed control to said train speed control transmitter means at said exitend of said track detection section.

24. A train speed control system for use in electrified territory, saidsystem having electrically continuous rails through which electricpropulsion return current flows and a train thereon having speed controlreceiver means to receive a train speed control signal from said rails,

(a) a plurality of bonds interconnecting said rails and spaced alongsaid rails, each of said bonds capable of equalizing the electricpropulsion return current in said rails and having a primary coil and asecondary coil inductively coupled to said primary coil, said primarycoil electrically connecting said rails, said bonds defining a pluralityof track detection sections, each section having an entrance end and anexit end, said bonds serving as a signal transfer means to and from saidrails,

(b) wayside transmitters electrically connected to a secondary windingof said bonds at alternate bonds,

(c) each wayside transmitter having at least two wayside receivers andrelated track relay means, said receivers tuned to the output of saidwayside transmitters and each electrically connected to a secondarywinding of the immediately adjacent bond, said wayside receiverscontrolling the actuation of said track relay means,

(d) train speed control transmitter means electrically connected to thesecondary winding of each of said bonds and controlled by said trackrelay means,

(e) said wayside receivers controlling said train speed controltransmitter means through said track relay 21 22 means so that when saidtrain enters said entrance transmitter means at said exit end of saidtrack deend of a track detection section and shunts said rails, tectionsection. said train speed control transmitter means at said entrance endof said track detection section ceases No references Citedto controlsaid train and there is a simultaneous 5 transfer of speed control tosaid train speed control EUGENE BOTZ Pfimw'y Exami'le"

1. A TRAIN SPEED CONTROL SYSTEM FOR USE IN A SYSTEM HAVING ELECTRICALLY CONTINUOUS RAILS AND A TRAIN THEREON HAVING SPEED CONTROL RECEIVER MEANS TO RECEIVE A TRAIN SPEED CONTROL SIGNAL FROM SAID RAILS, (A) FIRST, SECOND AND THIRD BONDS INTERCONNECTING SAID RAILS, EACH BOND HAVING A TRAIN SPEED CONTROL TRANSMITTER MEANS ELECTRICALLY COUPLED TO SAID BOND TO PROVIDE TRAIN SPEED CONTROL SIGNALS TO SAID RAILS, AND SAID SECOND BOND HAVING A WAYSIDE TRANSMITTER ELECTRICALLY COUPLED TO SAID SECOND BOND, (B) SAID FIRST AND THIRD BONDS HAVING WAYSIDE RECEIVER TUNED TO THE OUTPUT OF SAID WAYSIDE TRANSMITTER AND ELECTRICALLY COUPLED THERETO TO CONTROL SAID TRAIN SPEED CONTROL TRANSMITTER MEANS SO THAT WHEN SAID TRAIN PASSES SAID FIRST BOND AND THEN SAID SECOND BOND, SAID TRAIN SPEED CONTROL TRANSMITTER MEANS AT SAID FIRST BOND AND SAID SECOND BOND RESPECTIVELY CEASE TO CONTROL SAID TRAIN AND THERE IS A SIMULTANEOUS TRANSFER OF SPEED CONTROL TO SAID TRAIN SPEED CONTROL TRANSMITTER MEANS AT SAID SECOND BOND AND THEN SAID THIRD BOND TO THEREBY PROVIDE A CONTINUOUS SPEED CONTROL TO SAID SPEED CONTROL RECEIVER ON SAID TRAIN. 